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FORT COLLINS, Colo. -- Colorado State University researchers are playing a part in groundbreaking studies involving prolonged space travel. Their co-called guinea pigs are astronauts Scott Kelly and his twin brother, Mark.

He saw his brother for the first time since blastoff last year Wednesday night at the Johnson Space Center in Houston. There, the two will undergo days of testing that is in conjunction with never-before-done research at CSU.

The twin brothers share the same DNA. But CSU scientists will study if their blood is now different after Scott Kelly spent nearly a year in space while Mark Kelly was on Earth.

"The study is part of what they call the 'Twins Study,'" said CSU professor Susan Bailey. "We are getting blood supplies from both of the twins."

They got the brothers' blood before Scott Kelly traveled to space, while he was there, and now that he's back.

"We'll get samples again, starting this weekend," she said.

The study will determine how Scott Kelly's chromosomes changed in space while exposed to higher levels of radiation and stress from living in a weightless box, also known as the International Space Station

Their focus is a telomere on the chromosome.

Think of a shoelace as a chromosome. The end is called a telomere. It's a protective cap on the chromosome that keeps it from unraveling, and when it disintegrates, it can have a profound impact on a person's health on longevity.

"Our hypothesis is the stresses involved in space flight will act to accelerate that process for Scott Kelly. So he'll be aging more quickly," Bailey said.

And with age comes degenerative diseases such as dementia, heart disease and cancer. But the study has broader impacts than just space travel.

"If we could figure out a way to keep telomeres going for a longer period of time, we might be able to expand life span," Bailey said.

All thanks to twin subjects who are proving twice is nice when it comes to moving mankind forward.

There are nine other ongoing studies involving the Kellys, including their immunity, the microorganisms in and on their bodies, and the sequence of their DNA.